Highway traffic signal



March 13, 1934. W Q NElN m- AL 1,950,741

HIGHWAY TRAFFIC SIGNAL Filed May 31. 1929 Patented Mar. 13, 1934 UNITEDSTATES PATEN'U OFFICE HIGHWAY TRAFFIC SIGNAL William C. Nein and ThomasW. Varley, New

1 Claim.

This invention relates to the control of trame signals on highways wherethe main highway signals are normally indicating for clear tramocontinuously, and the cross street signals are norm mally indicating forstop continuously.

To allow for cross street traffic to talee place, a vehicle on a crossstreet when approaching a main highway causes the traffic signals toreverse and indicate clear for the cross street and stop for the mainhighway. After the vehicle has passed away from its position of control,the trahie signals return to normal. devices may be used so that asecond vehicle wishing to pass over the main highway, will not cause asignal change until some definite time has elapsed since a previouschange.

The object of the invention is to provide 'apparatus such that the'desired objects may be obtained when the control of the traffic signalsis by the use of thermionic vacuum tubes and oscillating currents ofelectric energy, the desired control being effected by the change ofoscillation of the currents.

In carrying out the invention, advantage is taken of the change of platecurrent to a tube when the electric oscillation changes in energy as avehicle or metallic mass passes a part of the circuit carrying theoscillating currents.

A control between the vehicle and the traflic signals is thus obtainedby proximity of the vehicle to a device along the highway.

In the accompanying drawing which illustrates the invention, ,Y

Figure 1 is a diagrammatic view showing a thermionic tube with itssource of energy and its electric circuits together with a pair ofwheels representing a vehicle or moving metallic mass.

Figure 2 shows a main highway and cross street with its traiiic signals,in this case light signals together with a part of the electric circuitscarrying electric oscillations placed in the roadway of the cross streeton either side of the main .highway The operation of the device is asfollows: Referring to Figure 1: v A thermionic vacuum tube 4 has itsfilament 5 heated from a source, in the case 115-volt, 60- cycle,through a lamp 6 as a resistance.

Across filament 5 is a resistance '7 adjustable to give proper filamentcurrent.

Across filament 5 is also a resistance 8 with a center tap 9 to give aconvenient return for the grid circuit of the tube. The grid 10 connectsthrough grid leak 11 and condenser C1 to a tuning coil 12 and itscondenser C2 and then to center tap 9. The plate 13 connects throughchoke 1i and relay 1 to the line side of lamp 6. The plate also connectsto its tuning coil 3 and its condenser C3 by a by-pass condenser C5.

'With the two coils 12 and 3 tuned to the same 6U frequency, the tube 4will cause oscillating currents to ow in the tuned coils 12 and 3. Toassist this eect a condenser C4 connects grid lli to plate i3.

As the circuit currents are oscillating, the plate current through relayl is less in amount than when the currents of the tuned coils 12 and 3are not oscillating.

The tuned coils 12 and 3 can be used at maximum oscillating valuenormally, and at less than 'Z0 maximum value when coil 3 for example isthrown less in tune by a passing vehicle 2 or the tuned coils 12 and 3can be used at minimum oscillating value normally and at more thanminimum value when coil 3 is thrown into better tuning 75 by a passingvehicle 2.

In the diagram shown with vehicle 2 over coil 3 which is embedded in theroadway, the tuned coils 12 and 3 are at a high value of oscillatingcurrent and the relay 1 is at 'open circuit due to 80 lowering of plate13 current. i l

The contacts 4 and 5 of relay 1 are closed causing signal lights G2 andR2 to indicate by current from, in this case, a battery 14. G2 and Rzcontrol signals to stop for main highway and to clear for cross street.

As vehicle 2 moves away from coil 3, current in coil 3 falls in value,plate 13 resumes normal high value of current through relay 1 causingrelay 1 to open contacts 4 and 5 and close contacts 4 90 and 6 givingcurrent to signal lamps G1 and R1, to indicate resumption of clear formain highway and stop for cross street- This construction of applicantshas the feature that the control of the resonant circuit, which resultsin the control of the signal, is by varying the magnetic induction whichis brought about by the passage of the metallic mass on the vehicle andis effective independently of any static induction and thereforeprovides a means for operating the devices buried in the roadway,notwithstanding the burying of the device shields it from eiect by thestatic induction occasioned by passing persons or other bodies than themetallic mass on a. vehicle which is capable of changing the magneticinduction as distinguished from the static induction. The device is onlyoperated therefore, as intended, by passing vehicles and is preventedfrom false operation by passing pedestrians, animals and the like.

circuits including an inductance coil beneath the surface of the roadwayand adapted to have its inductance varied by variation in its magneticinduction by the passage of a vehicle carrying a metallic mass inproximity thereto, thereby varying the resonant condition of the lastmentioned circuit and consequently varying the oscillatory character ofthe tube, and means for operatively relating said tube to said signal.

WILLIAM C. NEIN. THOMAS W. VARLEY.

